Columbia Presbyterian Medical Center's (CPMC) Division of Cardiothoracic Surgery is committed to becoming a Clinical Center in the Network for Cardiothoracic Surgical Investigations in Cardiovascular Medicine. We believe that our program is ideally suited to participate in this Network for the following reasons: our surgeons and interventional cardiologists maintain a large, diverse caseload; collectively, our investigators are among the leading innovators in nearly every area identified by the recently convened NHLBI/Cardiac Surgery Working Group as appropriate for study within the Network; our group is experienced in all elements of clinical evaluative research, including clinical trial design, protocol development, regulatory submissions, clinical coordination, patient recruitment and enrollment, data management, and quality assurance; and our center has repeatedly demonstrated the ability to recruit patients into clinical trials with a broad range of disease states as well as a diverse population, in terms of socioeconomic status, race, and ethnicity (with particular emphasis on the Hispanic population). We propose two randomized clinical trials with potentially important implications for clinical practice and public health that would be best completed as part of this proposed network: (1) to compare clinical outcomes following mitral valve surgery (MVS) with and without endocardial surgical ablation in patients with a history of continuous atrial fibrillation (AF) and (2) to evaluate the clinical benefits of optimized perioperative biventricular pacing (BiVP) versus no pacing (NoP) in patients with left ventricular dysfunction and intraventricular conduction delay undergoing open heart surgery (OHS). Also, included in this application is a proposal for the Clinical Research Skills Development Core. Lay abstract: Further advances in the treatment of heart disease are predicated on rigorous evaluation of various treatment options and the development of new treatment technologies. Creation of a clinical trials network will be an important advance in forstering this culture of rigorous scientific evaluation. (End of Abstract)